Overcenter snap device



Feb. 10, 1953 H. MILLARD 2,627,754

OVERCENTER SNAP DEVICE Filed Oct. l5, 1949 INVENTOR.

Patented Feb. 10, 1953 UNITED STATES PATENT OFFICE OVERCENTER SNAP DEVICE Harper Millard, Freeport, Ill., assignor, by mesne assignments, to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application October 15, 1949, Serial No. 121,574

12 Claims.

a snap acting spring system of the above character having improved operating characteristics as compared to existing comparable systems.

Another object of the invention is the provision of a snap acting spring system having greater stability and better balance characteristics during operation of the spring system than comparable existing systems.

Another object of the invention is the provision of a snap acting spring system having novel means for mounting the stressed members of the system.

Another object of the invention is the provision of a snap acting spring system of the above character employing spaced stressed members having novel means for simultaneously moving the spaced stressed members through an axis of maximum stress to actuate the spring system.

Another object of the invention is the provision of a snap acting spring system of the above character that is simple to construct, that is positive in its action, and that is relatively inexpensive to produce.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which- Figure 1 is a sectional view taken along the longitudinal axis of a snap acting switch, embodying the present invention, with the movable contact in an upper position;

Fig. 2 is a plan view of the switch shown in Figure 1 with the plunger and cover removed;

.Fig. 3 is a sectional view similar to Figure 1 showing the movable contact in its lower position; and

Fig. 4 is a transverse sectional View of the switch. taken along the section line 4--4 of Fig. 3.

Referring now to the drawings, the invention is shown embodied in a snap acting spring system for an electric switch. Asshown in this embodiment the spring system is mounted in a housing II of suitablev insulating material and comprising a bottom or base I2 for supporting the spring system and a cover I3 detachably secured to the bottom I 2 and defining therewith a chamber I4 for receiving the spring system.

The spring system comprises spaced tension members I6 interconnected at opposite ends by suitable cross-pieces I8 and I9, a compression member I1, and a bridging member 20. The comm crosspiece I8 interconnecting the tension membersv I ii. The stem is secured on the shoulder 21 pression member is connected at one end with the crosspiece I8 to dene an end carrying a movable contact 2I free to move between opposed positions, dened by upper and lower stops. The upper stop is formed by an L-shaped member 24 having a stem 26 supported on an upwardly facing shoulder 21 formed in the chamber I4 adjacent one side of the housing and an arm 28 offset withrespect to the stem 26 and overlying the by connecting members including a tubular portion 29 of an insert (not shown) molded in the bottom I2. The insert is shaped to receive a screw (not shown) providing a terminal at the bottom of the housing accessible for connection to an external circuit. A rivet 30 extending through the arm 28 defines a contact positioned to be engaged by the movable contact 2| when the latter is in its upper position as shown in Figure 1. The lower stop is formed in a similar manner by a generally L-shaped member 3I having an arm 33 carrying a stationary lower contact 38 and a stem 32 secured to an upwardly facing shoulder 34 formed in the chamber I4 onv the side thereof opposite to the shoulder 21. The stem 32 is likewisesecured in place by connecting means 36 including a metal insert passing through vthe base and receiving a terminal screw 31 to define a terminal at the bottom of the housing for connection to an external circuit.

One phase of the invention is concerned with novel means for mounting the tension members I5 and compression member I1.' In this embodiment of the invention a single anchor bracket 39 forms the mounting for both the tension members I6 and the compression member I1. The bracket includes a pad 4I at one end shapedto seat upon a shoulder 42 formed at one end of the chamber I4. The pad 4I is secured to the shoulder 42 by deforming the end of the tubular portion 43 of an insert 44 moldedv in the bottom I2, y a screw 45 threaded into the insert defining a terminal for connection to an external circuit.'-

Mounting the pad 4 I in the above manner in effect provides a cantilever mounting for the bracket 39 in the chamber I 4 so that the bracket extends inwardly toward the center of the chamber.v The crosspiece I9 interconnecting the tension members I5 rests onthe pad 4I in face to face relation therewith and is secured in place by the tubular portion 43. Adjacent the pad 4I is a shoulder 46 shaped and positioned for engagement by the inwardly facing edge 5l) of the crosspiece I9.y

the shoulder 46 in 'this instance being, OrmeS- by offsetting the bracket adjacent its end to produce the pad 4I as best seen in Figs. 1 and 3.

The free or unsupported end of the bracket 39 has an upstanding leg 49 formed by bending the bracket downwardly in spaced relation to its free end as shown at 48 and upwardly directly adjacent its end with the legs 48 and 49 in spaced relation as shown at 5I. The leg 49 is provided with a groove 52 for pivotal reception of the free end of the compression member I'I. The distance between the recess 52 and the shoulder 4B is somewhat greater than the distance between the end of the compression member II and the edge 50 when kthe spring is dis-A posed flat and consequently whentheispringl is mounted the member I'I is stressed in compression and the members I6 are stressed in tension; The recess 52 is also located below a line joining the free end I8 when in its upper position, as shown in Figure l, and the pad 4I so that aportion ofthe tension members may be depressed ltoa position below the recess and thereby eiectsnap movementl of the mobile contact.

The bridging vmember 2Il'is .connected at opposite ends with the tension members I6 (in this instance being integral therewith) at a position between the shoulder 46 and the pivotal recess 52. In general the dimensions of the bridging memberV 29 aresuch as to provide a relatively rigid member between the tension members IB; however, the width of the bridging member is such that it may be receivedbetween the legs 48 and 49 formed on the bracket 39when the tension members I6 are moved to actuate the spring system.

The plunger 54 comprises a stem 56 and a head`51. The stem 55 is slidably received in the cover` Iii-and the head Slis formed with a skirt 59'having a surface on one edge shaped to conform to the surface of va shoulder EI formed on the cover I3 so as to prevent rotation of the plunger` during reciprocation. The head is formed'with a rounded projection 62 extending transversely of the tension members I6 and shaped to engage the bridging member 20. The projection 62 is shaped so that the contact between the bridging member Aand the plunger is a: line` contact that extends `over a considerable length of the bridging member as shown in Fig. 4.

To actuate the switch the plunger 54 is moved downwardly causing the projection-62 on the plunger 54to urge the bridging member 20 and thetension members I6 downwardly until the line of action or stress line of the tension mem-- bers lmoves across or past the compression pivot point dened by recess 52. Thereupon the contact V2l snaps from engagement with the contact 3Il-toengagement with the contact 38. The position of the parts when the contact 2I engages the contact 38 is shown in Fig. 3; As the plunger moves downwardly the bridging member 29 is received between the legs 48 and 49 to permit the required relative movement of the tension members Anecessary to eiect snap action of the spring system.V Preferably the tension and 'compression members are biased so that they return to the-position shown in Figure 1 upon release of the actuating force. In so doing the tension stress'line is moved through the axis of maximum Astress and the contact 2l is moved with a snap action from engagement with the contact 38 to engagement with the contact 30.

Where vdesired portions of the tension members row portions 55 adjacent their mounted ends. The above construction is for the purpose of distributing stresses in the tension members I6 in a preselected manner to control the exure thereof as described more fully and claimed in an application of Robert M. Readeker, Serial No. 156,439,1iled April 17, 1950;

Pressure applied to the bridging member through the plunger 54 causes both tension members I6 to move simultaneously relative to the compression member. The bridging member also acts somewhat as a strut to prevent excessive ilexing of the .spring about the longitudinal axis of the spring and thereby serves to retard twistinglor turning of the tension members I5 as theyare moved to actuate the spring system. Thus one tension member is prevented from going overcenter before the other. This construction therefore produces a spring system which is stable and has good balance characteristics during its operation. The line contact of the plunger-54 with the. bridging memberl 53- tends to distribute the appliedforce over the length of the bridging'member. However, if `desired, the plunger may be constructed with two: depending points, one located neareach end of i the lineof contact. With the line contact-there is less tendency on the part of the bridging member to buckle thanV would be the case if .the force were applied `to asingleV point on thebridging member.

One advantage of the mounting means; for' the tension and compressionV members isthat the shoulder 45 engages the cross. member -I9 throughort a substantial portion of its length:` The stresses in the cross member are thus Adis-l tributed and the high stresses in the .tension members, such as when a single rivet of con-V ventional construction is utilized to hold the tension member, are avoided. The anchor bracket 39 is extremely simple to form and may be readily made as a single stamping. Consequently .itx can be made relatively inexpensively. The remaining parts of the spring system arev also of very simple construction and can also be-read-` ily made as stampings. The shape of th'e parts is such that the full width of the strip material from-which they are formed maybe utilized. Consequently there is very .little scrap. material.. in the productionv of 'this switch.y Due'to they fact that there is only-one anchor'groove re-. quired for-the compression.` member,y alinement problems, are eliminated. Since ythere is onlyI one compression .memberto vbe'seated inthe an.- chor groove very little work is required intheass-embly of this construction. In view ofithe above it is apparent that the production costof this snapV acting springzsystem is relativelylow.

I claim:

1. In a snap acting device, the combination .of spaced tension members interconnected at one end to form an end free tofmove between opposed i positions, a compression member disposed between said spaced members and interconnected at'v an end 'with said free end,:means iixedly mounting the opposite end of each tension member in spaced relation to each other, means mounting. the opposite end of. the compression member to have the line of stress in said tension member movable past the mounted end of the compression.-Y member, bridging means interconnecting said. spaced .tensioni-members intermediate. the ends thereofr and an actuator vengageable withsaid. bridgingmeans for movingthespaced members: to :movetthe tension-stress line.` across .thefcome pression stress line to move said free end between said opposed positions with a snap action.

2. In a snap acting device, the combination of spaced tension members interconnected at opposite ends, one of said ends being free to move between preselectd positions with a snap action, a compression member having one end interconnected with said free end, means for mounting the opposite end of said compression member, means dening a stationary mounting for the other end of the tension members in spaced relation to one another, rigid bridging means interconnecting said tension members at a position between said mounting means for the tension and compression members, and a plunger positioned to engage said bridging means to move said tension members for moving said tension stress line across said compression stress line to move said free end between said positions, said plunger being shaped to have line contact with said bridging means to distribute the applied force over a substantial length of the bridging portion.

3. In a snap ac-ting device, the combination of spaced tension members interconnected at opposite ends, one of said ends being free to move between preselected positions with a snap action, a compression member having one end interconnected with said free end, means for mounting the opposite end oi said compression s member, means dening a stationary mounting for the other end of the tension members in spaced relation to one another to have the line of stress in said tension members movable past the mounted end of the compression member, bridging means interconnecting said tension members at a position between said mounting means for the tension and compression members and a plunger engageable with said bridging means to effect simultaneous movement of said tension members to move the tension stress line across the compression stress line to move said free end between said positions, said plunger having an end portion extending between the tension members and shaped to have line contact with said bridging means to prevent buckling of the bridging means upon application of force to the plunger to move the tension members.

4. In a snap vacting device, the combination of spaced movable tension members, spaced crosspieces interconnectingsaid tension members at opposite ends thereof, a compression member disposed between said tension members and interconnected at one end with one of said Vcrosspieces to form an end free to move between opposed positions and having its opposite end spaced from the other crosspiece, stationary means for mounting the opposite end of the compression member, stationary means including shoulder means engageable with said other crosspiece and dening a stationary mounting for said spaced tension members, said shoulder means engaging said crosspiece throughout a substantial portion of its length and positioned to have the tension stress line movable through the compression stress line, and an actuator between said mounting means for the compression and tension members for moving said tension members to move the tension stress line through the compression line to move said free end between said opposed positions with a snap action.

5. In a snap acting device, the combination of spaced movable tension members, spaced crosspieces interconnecting said tension members, a compression member disposed between said tension members and -interconnected at one end'.v

with one of said crosspieces to form an end free to move between opposed positions and having its opposite end spaced from the other crosspiece,

an anchor bracket. for said tension and compres Y sion members having a xed shoulder positioned to engage said other crosspiece and defining thereat a mounting for said spaced tension members and having a portion spaced from the shoulder disposed between said tension members and having a recess for pivotally receiving the opposite end of the compression member to stress the latter in compression and to stress said tension, members in tension and means for moving said tension members to move said tension stress line across the compression stress line to move said free end between said opposed positions with a snap action.

6. In a snap acting device, the combination of spaced movable tension members, spaced crosspieces interconnecting said tension members adjacent the ends thereof, a compression member disposed between said tension members and interconnected at one end with one of said crossthereof, bridging means extending between saidv spaced tension members intermediate the ends thereof, and a plunger having line contact with said bridging means for moving said tension members to move the tension stress line through the compression stress line to movesaid free end between opposed positions with a snap action.

7. In a snap acting device, the combination of spaced movable tension members, spaced crosspieces interconnecting said tension members adjacent the ends thereof, a compression member disposed between said tension members and interconnected at one end with one of said crosspieces to form an end free to move between opposed positions and having its opposite end spaced from the other crcsspiece, a stationary bracket including a mounting portion positioned to rigidly mount said spaced tension members at one endV thereof and a mounting portion shaped to mount said compression member to form Withsaid tension members a snap spring'system having an axis of maximum stress, said bracket having a central portion disposed at one side of the plane of the mounted ends ofthe tension and compression members, bridging means extending between said spaced tension `members intermediate the ends thereof shaped to pass between said mounting portions, and plunger means having line contact with said Vbridging means for moving said tension members to move the tension stress line through the axis of maximum stress-to move said free end between opposed positions with a escapan tions and having its oppositefend. terminating short or the:v other crosspiece, a i bracket'. for mounting: said tension members inV vtension and said; compression member in.; compression, said..V

bracket beingzformed'with arearz shoulder pcrtion engaging; the; other of; said'V crosspieces. throughout 1.a A substantial portion of the length thereof i and forming: a stationary vmounting for u one. `end of said-, spaced .f tension members.. said bracket also being formed with a recess :for pivotally receiving saidnopposite ,end xof the;compres sion memberto stress the; latter in; compression, a.. bridging ,memberinterconnecting said rspaced tension members intermediate the lengths thereof, anda plungerxhavingline contact with said bridgingmember fordisplacng the tension memberstomove the tension stress line through theY compression .stress line to move. said c ireeiend between opposed positions with a snap-action.

10. In asnap acting device, the combination. ofA spaced: movable tension members, spaced cross: pieces interconnecting said tension members atV the ends-thereof, a compression member disposed between" saidl tension members and interconnectedat yone end'with one of said crosspieces to form an endifree to move between opposed positions and having its opposite end terminating shorttof'the other crosspiece, a bridging member interconnecting said .tension members intermediate -thelengths thereo, a vplunger contacting said bridging portion for displacing the tension members, and a bracketv for mounting thetension and.. compression members, said bracket beingformed.. Withfa, ,rearwardly-facing shoulder "engaging the other of saidcrosspieces iora substantial portion of the-.length thereof and. forming as stationary mounting for one end ofsaid spaced; tension,

ofi a-'pair of" spaced,i.. parallel.. coplanartension. members,l spaced 'icrosspieces interconnecting said..-

tensionmembers atzthe ends .'thereof, a` compressionV member disposedbetween said tension mem-` bers and interconnected at one end with one of said" crosspieces to form an end free to move between opposed positions and having its opposite; end terminating a substantial distance short ofthe other crosspiece, means formi-nga pivotalmountingi said opposite end of the.

compression member, stationary meansfor mounting said'tension members atione endfin spaced relation comprising a --shoulder-` positioned between said tension members and engagingthe other of saidcrosspieces throughout. asubstantial portion of the length thereoa bridging member interconnecting said` tension, membersr and disposed intermediate said shoulderV for mounting-the tension `members and said pivotalv mounting for thecompression member, andaV plungenhaving line contact with said bridging member transversely ofthe tension members :for

displacing said bridging member to pass between said shoulder mounting for the tension members and said pivotal mountingfor the compression member. f

12. In a snap-acting device, the combination of spaced movable tension members, spaced crosspieces interconnecting. said tension. members, a compressionmember disposedV between said tension members and .interconnected ateneV end with one of said vcrosspieces to `form an Yend free to move between opposed. positions andhav.-

ing its opposite end spaced from` thevother.

crosspiece, ananchor. bracket for. said. tension and compression members .having arigidrshoule der shaped to engage the-other of said crosspieces and defining thereat a mountingforsaidspaced.

tension members and having a. portionspaced from the shoulder disposed between said tensionA members and having a recess forpivotally. receiving the opposite end. of the compression member to stress the latter in compression and to stress said tension membersin tension,.and.

means for relatively moving saidtension stress line andA said compression stress line to move said end between opposed positions Withasnapy action.

HARPER MILLARD.

REFERENCES CITED The following references 4are of record in the le of .this patent:

UNITED STATES .PATENTS 

